Electrodeposition of nickel from an acid bath



Patented July 4, 1950 Hem-y Brown, Detroit, Micln, minor to The 'Udyiite Corporation, Detroit, 511011., a corporation of Delaware No Drawing. Application October 31, 1945, i

I Serial No. 625,963 r 4 Claims. (Cl. 204-49) 2 This invention relates to the electrogleipogttiri TABLE 111 of bright ductile plate from aqueous ac c c e baths, The N alklll 7 111213320122 sand qumolzmum This object can be accomplished by the addition of certain organic compounds containing unsaturated linkages and selected from the class of N-alkyl pyridinium pyrazoles and quinollnium pyrazoles to acidic nickel baths such as those listed in Table I, and containing in addition TABLE I Current Den- BamNo' 10150453120, NiCl,.6H,O, N113, Fonmm'a'h 'lgi np, pH slmAmm/sq g./l. g./l. g./l. it.

200-500 45 HBO 40 75-100 2-0 -75 300 an" -150 1-5 10-100' 50-200 100-250 on 15-100 1.5-0 10-55 200-300 45-75 H macaw-mum..- 75-100 2-0 10-15 200-300 45-100 8-50 11,1;o,,40-sat..- 75-150 2-0 10-35 50-100 45-100 8-100 do 75-100 2-0 10-55 45-100 50-150 do 75-160 as 10-100 200-250 100-150 8-15 11,130,, 40-50..- 75-100 2-0 10-85 o-benzoyl sulflmide and/or one or more of the compounds of the classes of compounds listed in Table II, and hereinafter called the aromatic sulfon-compounds which all contain the essential grouping In Table III are listed a number of N-alkyl pyridiniumand quinolinium-pyrazoles and their optimum concentrations in the acidic nickel baths when used in conjunction with o-benzoyl sulfimide and/or one or more of the aromatic sulfon compounds of Table II, also dissolved in the bath.

TABLE II 0 timum Aromatic sullen-compounds one. in

Bath in all.

o-benzoyl sulflmide (saccharln)...- 06-3 g./l and up to sat sodium o-henzoyl sulfimlde.. 0. Crchloro-saccharin 0.5-3 (3511.3. 7-cl1loro-saccharln 0.5-3 (sat. (i-bromo L in 0.5-3 885.). G-aldehydo-sacchann--- 0.5-3 sat). "disaccharin 0.5-2 (sat.). benzene snll'onamide-.. 0.5-2 (set). 0- or ptoluene sulionamidc. 0.5-2 (sat.) m-benzene disullonamide..- 0.5-1 (sat diplienyl sulione sulionic aci l-4. 1,5 naphthalene disullonic acid 1-3. m-henzene disulionic acid l5. methgxy naphthalene sulionic 3. am 5.

chlor naphthalene sulionic acids 3. p-brom benzcnesulionic acid 3-6. couniarin sulionic acld..... l-4. benzaldehyde sullonic acids v 2-4. di-aldehydo ben7 .ene s ullonlcacid s. l-4.

p-tolgene sulfimc acld (sodium 0.02-1. benigne sulfinic acid (sodium 0.02-1.

1 Prcfcrabl to be used in the smaller concentration values in conjunction wit the other compounds irom l to 19.

O t. 00110. fl g 13mm,

v g./l.

1 N-ethanol (fi-hydroxy ethyl 4-nitro-5- 0.002-.00B (-3 pyridinum) pyrazcle chloride.

CzHcOH NO, H /Cl (g Y H g l4 lilll HC 6 ,3 5 2 H H g 2 N-ethanol, 3-nitro-5-(-3" pyridinium) 0.002-.008

pyrazole chloride. 3 ethanol 3,4-dl nitro-5-(-3 pyridinl- 0.002.008

11111) p razole chloride. 4 N-fl,m, ihydroxy propyl-4 nitro-5-(-3- 0. 002-. 008

pyrldlnium) pyrazole chloride. 5 N-acetonyH nitro-5-(-3 pyridinium) 0.002-.008

pyrazole chloride. 6 N-ellyl-4 nitro-5-(-3-pyrldinium) pyra- 0.002-.008

role bromide. 7 N-butanoH nitro-5-(-3-pyridinium) 0.002-.008

pyramle iodide. 8 N-ethyl-5-(3-pyridinium)pyrazolc sul- 0002-.008

a 0 N-ethanol-5-(-3-isoquinolinium pyra- 0.002-.008

zole chloride. 10 N-ehtlhaziol-l-b '-quinolinium) pyrazole 0.002-.008

c or e. 11 N-methyl acetate-4-nitro-5(-3'-pyridlni- 0.002.008

um) yramle chloride. 12 N-acet c acid (or betaine iormH-nitro- 0. 002-.008

6(-3-pyridinlum) pyrazole chloride.

fact, around twelve carbon atoms if substituting groups such as hydroxyl, carboxyl, sulfonic, etc. are also present on the N-alkyl chain. However, at about seven carbon atoms as a pure alkyl chain (slightly more if the chain is branched) the solubility becomes inconveniently small, and as an N-alkyl chain of eight carbons is reached, the chain will tend to confer upon the compound the properties of a cationic wetting agent or detergent which will tend to agglomerate with any anionic detergents or wetting agents if the latter are present (for the prevention of pitting).

The o-benzoyl sulfimides The o-benzoyl sulfimide type of compound (see United States Patent 2,191,813) when dissolved in acidic nickel baths greatly reduces the grain size of the plate and greatly increases the luster, and on clean buffed metal surfaces there is deposited bright ductile adherent nickel plate even though the plate is several thousandths of an inch in thickness. Furthermore, after the maximum effect is produced on the plate by the o-benzoyl sulfimide type compound, there is practically no further ect obtained by substantially increasing the concentration. Whereas, with the active (with respect to the nickel plating) unsaturated organic compounds such as those of Table III added to the plain nickel baths very marked changes are produced with increasing concentrations above the optimum amounts of these materials.

Beside? the very pronounced brightening eifect produced by the o-benzoyl sulfimide type compounds, they act in a remarkable manner to decrease the sensitivity of the plate to an exceedingly large number of foreign substances (especially organic) added to the bath. They act to decrease the degree of embrittlement of the plate caused by the reduction and/or plating out of excessive basic salt inclusions, colloidal materials, foreign metals, organic materials.

The results obtained when certain-unsaturated compounds are added to the acidic nickel baths containing an o-benzoyl sulfimide type of compound dissolved therein are very striking from the standpoint of the rate of brightening and the brilliance of the plate when compared to the results obtained with either material alone in the bath. Of unusual effectiveness in obtaining exceedingly bright yet ductile plate in conjunction with o-benzoyl sulfimide type of compounds in acidic nickel sulfate or nickel chloride baths or such mixtures as the Watts type bath, are the unsaturated compounds of Table HI.

Without the o-benzoyl sulfimide type compounds present in the bath, the unsaturated compounds of Table III give fine grained cloudy plate at very low concentrations and at slightly higher concentrations give rather dark, brittle, easily stained, poorly adherent plate. In this way, these unsaturated compounds of Table III act similarly in the acidic nickel baths to certain other organic compounds containing unsaturated groups, for example, furfural, crotonaldehyde, benzaldehyde, allyl alcohol, allyl amine, nitromethane. These compounds also-cause dark, easily stained, brittle, poorly adherent plate when used alone in the acidic nickel baths. The introduction of a soluble o-benzoyl sulfimide will make the plate brilliant, of good color, adherent and ductile. That is, of course, within certain limitsof concentration of the active unsaturated compounds for very large excesses of the latter will finally overshadow to a certain extent the beneficial effects of the o-benzoyl sulfimide.

Though unsaturation appears to be a very im portant property of these active brighteners, it does not mean that any compound containing an unsaturated linkage will be a brightener in the presence of o-benzoyl sulfimide. For example, benzotriazole does not produce bright ductile plate in the presence of o-benzoyl sulfimide, but yields a dark very brittle plate in even very small concentrations.

The o-benzoyl sulfimide (and similar compounds) greatly retards the rate of depletion (adsorption, reduction, or plating out) of the above referred to unsaturated brighteners. Also, if the plates 'are analyzed for carbon content, less carbon is found in the plate than if the o-benzoyl sulfimide (or similar compound) is absent from the bath. The life of the o-benzoyl sulfimide type of compounds-in the bath is extremely longer than that of the unsaturated compounds like furfural, crotonaldehyde, allyl alcohol, the N- alkyl pyridinium pyrazoles, etc. The active unsaturated compounds are reduced or plated out at a preferential rate as compared to the nickel ions. It seems that traces of the o-benzoyl sulfimide type of compounds are reduced (the sulfur going to a valence of 2) and plated out at the nickel cathode and poisons or partially poisons the nickel with respect to the ease of adsorption, reduction and plating out of the unsaturated brighteners. It would seem that the double bonds are important in an adsorption of the unsaturated organic compounds by surface atoms of freshly deposited nickel with their unsatisfied bonds extending outward, and is similar to the postulated adsorption process for catalytic nickel in certain reactions (hydrogenations and decompositions) involving unsaturated organic substances. The tendency for nickel to link to unsaturated compounds is seen in the compound nickel carbonyl. Even with the o-benzoyl sulfimide (and the compounds of Table II) unsaturation (the carbon double bond) plays an important role.

The aryl sulfinates (Table 11, compounds 20, 21) are very useful to prevent the low current density areas from becoming dark due to the presence of an excess of such ions which preferentially plate out such as zinc, copper, lead, etc. It is at the low current density areas where the first excess of active materials which plate out preferentially usually shows up. Thus, one of the best uses of the sulfinates is in small amounts, such as 20 mg./l., in conjunction with o-benzoyl sulfimide or the similar compounds of Table II. Too large concentrations of the sulfinates will slow up the rate of brightening produced (at the higher current densities) by the active brighteners (i. e. crotonaldehyde, a,u.,B, trichlorobutyraldehyde hydrate, N-ethanol pyridinium nitro pyrazole, zinc, etc.), evidently, because of its great effect in retarding their plating out. Thus, with the small amount of sulfinates also present (besides the o-benzoyl sulfimide compounds or naphthalene sulfonates, diphenyl sulfone sulfonic acids, or benzene sulfonamides, etc.), the acidic nickel baths can tolerate larger quantities of the active materials which plate out preferentially, without misplating or obtaining dark plate at the very low current density areas; thus, the useful bright platerange is extended.

The use of the sulfinates in many of the commercial baths is therefore often advised because the nickel baths usually contain small percentages of such metals as zinc, copper, iron, lead, which may enter the nickel bath as impurities in nickel salts or anodes, or during the nickel plating of, for example, copper plated zinc-base articles, etc. However, in the cases, as the last mentioned one, where often such impurities are continually increasing in the bath, it is by far best to circulate the solution through an eificient small "dummying tank for continuously plating out these impurities at low current densities and high solution velocity.

The N-alkyl pyridiniumand quinoliniumpyrazoles The compounds of Table III in conjunction with an o-benzoyl sulfimide type compound (or its Na, Ni, Co, etc. type salt) will produce brilliant ductile nickel plate with an amazingly high rate of brightening over such matte surfaces as 180 emery polished steel. Furthermore, this combination of brighteners gives practically equal brightness and rate of brightening in all of-the acidic nickel baths given in Table I or in such nickel baths containing other ions or buffers such as bromide, formate, acetate, citrate, tartrate, gluconate and perchlorate. oxidizing anions, such as nitrates and especially chromates which markedly affect the cathodic processes, should be kept out of the bath. That is, the brighteners can be used in any acidic "grey nickel plating bath which is capable of producing thick, adherent ductile nickel deposits. For example, nickel sulfamate in whole or in part may be used, that is,

mixtures with nickel sulfate and fiuoborate,-.etc.

Nickel sulfamate does not appreciably corrode nickel anodes, and hence a certain amount of chloride or fluoborate or both should be used.

However, it must be kept in mind that free sulfamic acid slowly hydrolyzes to ammonium sulfate in the warm baths, and concentrations of ammonium salts above about g./l. render the nickel plate very brittle from warm baths.

Sodium or magnesium, though not desired in general, can be tolerated to rather high concentrations in these bright plating baths. They affect the rate of brightening a little, but not the ductility unless very large amounts are used. Ammonium salts, especially in warm baths, seriously affect the color and ductility of the plate in other than small amounts. Metal ions like Zn, Cd, 'I'l which plate out with the nickel and act as brighteners may be used with the compounds of Table III in conjunction with o-benzoyl sulfimide, but a little less of each should be used or the recesses (low current density areas) will be quite dark, necessitating all the more a small amount of a benzene sulfinate to keep the low current density plate bright and adherent.

In the Watts type of bath (high nickel sulfate content) c. g.; such as No. 1 in Table 1, instead of o-benzoyl sulfimide, it is effective to use aryl sulfonamides such, e. g., as benzene meta disulfonamide, benzene sulfonamide, toluene sulfonamide, together with the compounds of Table III. Also aryl sulfonates such, e. g., as naphthalene monoand di-sulfnnates and benzene meta disulfonic acid (preferably in high concentrations, i. e., g./l.) may be used instead of o-benzoyl sulfimide. In a nickel sulfate bath this difference between o-benzoyl sulfimide and the others just mentioned is not especially pronounced, but when the nickel chloride concentration in such a bath is increased (while the nickel sulfate is correspondingly decreased) from, for example, about 30 g./l. of nickel chloride to 250 g./l., the difference becomes very manifest as to the superiority of o-benzoyl sulfimide both from the standpoint of high brightness, adhesion and ductility. This is made even more clear in plating bright nickel depositsof 0.001-.003 inch thick. This is true not only whenused alone, but also when other brighteners such asthe compounds of Table III or (1,1149, trichlorobutyraldehyde. hydrate, phenosafranine, etc. are present is the acidic nickel baths. This does not mean the arylsulfonamides, such as the benzene monoor disulfonamides, the aryl sulfonic acids such as naphthalene sulfonic acids or the diphenyl sulfone sulfonic acids are of no value in conjunction with the unsaturated brighteners in such acidic nickel baths as the high chloride bath (#2, Table I). They are beneficial-but not nearly as much as the o-benzoyl sulfimide compounds. In general it is preferred to use two compounds from Table H, i. e., o-benzoyl sulfimide and another compound such as p-toluene sulfonamide or sodium p-toluene' sulfinate (at 20 mg./l.).

In the plain nickel chloride bath where the range (of temperature, concentration and pH) of obtaining ductile white deposits are much more limited and critical than in a nickel sulfate or Watts type bath the results obtained by the addition of just 1-2 g./l. of o-benzoyl sulfimide are more striking than in the Watts bath. In the normal operating ranges of the chloride bath where darkish brittle plate is obtained (due probably to basic salt inclusions) there is obtained instead bright ductile plate.

In a previous application (Serial No. 573,303, filed January :17, 1945, in which has become abandoned) the excellent brightening action of the 3- or 4-nitro-5(-3'-pyridyl) pyrazoles in conjunction with the o-benzoyl sulfimide com pounds was disclosed. However. these compounds are only very slightly soluble (approximately 5 na/1.) in the acidic nickel baths of Table I, and while their hydrochloride salts are more soluble, the latter are nevertheless unstable, disassociatzing at the higher pH values of the baths (4.5-5.5), with the very weak bases (i.' e., the above 3- or 4-nitro-5(-3 pyridyl) pyrazoles) "tending to separate and precipitate out in a finely divided state. On the other hand it was found, for example, that the reaction product of methyl chlor-acetate or ethylene chlorohydrin with these compounds produced derivatives (compounds 1, 2, 3, 11 and 12 of Table III. As far as we can find in the organic chemistry literature these particular derivatives listed have not hitherto been prepared) that were about a thousand times as soluble in the bath, and were stable and did not salt out at any of the operating temperatures and pH values of the baths, and gave more ductile plate, and were less critical in excessive concentrations with respect to ductility, adhesion and bright throwing powder." Thus, due to the high solubility of the compounds of Table III and similar N-alkyl derivatives in the baths, they are easily added to the nickel baths even while articles are being plated because comparatively little stirring is necessary to distribute the brightener fairly uniformly throughout the bath, and hence the appropriate concentrations are easily maintained.

It was found that the N-acetic and the N- ethanol (and others such as N-propanol) pyridinium nitro pyrazoles used in conjunction with o-benzoyl sulfimide and/or benzaldehyde monosulfonic acids gave plates that were remarkably free from pitting without the use of any auxiliary wetting agents, and also that the plates were remarkably ductile (especially with o-benzoyl sulfimide) for such high brightness (more ductile, in fact, than plate obtained from the plain high chloride bath operated at the same pH and temperature). Ductility is of great importance for outdoor use of bright nickel where due to wide temperature changes and strains, crack lines will develop in insufficiently ductile nickel, with comequent failure in corrosion protection. To obtain a somewhat further improvement in ductility of the plate, especially at the higher current densities, it is advisable to use an aldehyde of the type of ,a.p, trichlorobutyraldehyde hydrate (see United States Patent 2,321,182) in conjunction with one of the compounds of Table III and o-benzoyl sulfimide. In fact, these combinations give the most ductile brilliant plate of any combinations yet tried, especially in the high chloride baths such as Example (see below). The very, excellent rate. of brightening obtained with the compounds of Table III in conjunction with o-benzoyl sulfimide makes it possible to plate over about .0002" to .0004" of dull (but smooth) copper obtained from the standard cyanide copper baths, and still obtain brilliant nickel plate (.007" to .001" nickel plate), and it was found that such ratios of copper and nickel followed by a flash of chromium over steel articles such as hub caps and bumper guards, gives outstanding salt-spray protection to these ferrous articles.

Examples of preferred bright plating bath compositions are listed under Examples A, B, C. Bath C is used for highest current density plating, and also where highest anode current desities are wanted.

Example A Grams/liter NiSO4.6H2O 200-300 NiClzfiHzO 125- 45 H3303 40 o-Benzoyl sulfimide 1- 2 p-Toluene sulfonamide l N-Methyl acetate, 4-nitro-5(-3'-pyridinium) pyrazole chloride 0.002-.006 Temperature, 110-140 F. pH=3-5.0.

Example B Grams/liter NiSO4.6H2O 300 NiCh.6HzO 45- 60 HaBOa 40 p-Toluene sulfonamide 2 N-Acetic acid- 4-nitro-5(-3' pyridinium) pyrazole chloride a,d,,B, Trichlorobutyraldehyde hydrate 0.3-0.7

Temperature, 1l0-l40 F. pH=3.0-5.0.

Example 0 Grams/liter NiSO4.6H2O 7 5 NiCl2.5HzO 300 0 H3130: 40 o-Benzoyl sulfimide 1- 2 Sodium p-toluene sulfinate 0.02

N-Ethanol, 4-nitro-5 -3'-pyridinium) pyrazole chloride .003-.004 a,a,}3, trichlorobutyraldehyde hydrate Temperature, 110-140 F. pH=3-4.8.

The best cathode film bufier is boric acid, and

should be used in all of the acidic nickel baths values, i. e., 5-5.5 and are exceptional in prevent- I ing burning.

To prevent pitting, air agitation, or the use of compatible wetting agents which do not interfere with the ductility of the plate or the bright plate range can be used. With air agitation or any increased cathode or solution agitation less of the brighteners of Table III should be used, but not less of the o-benzoyl sulfimide. Examples of preferred wetting agents are: sodium lauryl a1- 16 acted with ethylene chlorohydrin, methyl chlorcohol sulfate (0.1-.5 g./l.), n-decyl benzene sulfonate (0.1-.5 g./l.) (pure nickel salt) and a few others.

The tank lining, if of rubber or plastic, must be of proper type and not release any chemicals such as anti-oxidants, aniline, accelerators, plasticizers, etc. to the bath, or the nickel plate may be dulled and/or severely embrittled.

In the high chloride or high fluoride (fluoborate) containing baths, no lead (coils, linings, etc.) should be used in contact with the baths, as lead is rapidly dissolved by such baths. Traces of dissolved lead acts as a brightener in conjunction with o-benzoyl sulfimide type compounds, but slight excesses cause dark plate (first in the low current density areas and then with greatly increasing lead concentrations practically the entire plate is dark and poorly adherent).

Other harmful materials which must be kept out of the nickel baths are certain soaps, saturated cationic detergents, drawing lubricants, bufling dirt, etc. All of these materials tend to make the bright plate dull and brittle.

The compounds of Table III are mutually compatible with a,,p, trichlorobutyraldehyde hydrate, phenosafranine, etc. It is important, however, not to use the full concentrations of each unsaturated brightener, as their effects are additive. This also applies to their use with inorganic brighteners such as Zn, Cd, Tl.

Cobalt (up to about 10 g./l.) in the bright nickel baths is definitely beneficial in making for somewhat brighter and more ductile high current density plate. This is especially true with obenzoyl sulfimide compounds present in the bath together with unsaturated compounds such as those of Table III and especially in the high chloride nickel baths. However, w s, trichlorobutyraldehyde hydrate exerts a similar beneficial efiect in concentrations of 0.3-.7 g./l. in these baths containing o-benzoyl sulfimide.

To obtain a, desirable bright plate, one or more of the compounds of Table 111 preferably is used in an amount within a range of from about 0.001 g./l. to about .02 g./l. of solution with one or more compounds of Table II in an amount within a range of from about .02 g./i. of solution to saturation, but the most desirable concentration of brightening compound or compounds from Table III will depend on the operating conditions of the plating bath such as, e. g., pH, temperature, particular compound of Table II present as well as the type of nickel salts present in the bath.

It is possible to use various substituting groups on the rings of the aryl sulfonamides, sulfonimides, sulfonic acids, sulfones and sulfinic acids, for example, methoxy, halogen, methyl, ethyl, ethoxy, cyano, aldehyde, vinyl, ally], small chain aliphatic nitro, small chain aliphatic hydroxy, and carboxylic and carboxylic' amide or imide (acid amide) groups.

It is interesting to note that the N-alkyl pyridinium pyrazoles (for example compounds 1,

2, 6, 11 and 12 of Table III( give very much more 1 Finally, it should be mentioned that while 4- nitro-5(-3' pyridyl) pyrazole (which was inter- 9 acetate, allyl bromide, etc. to give compounds 1, 6 and 11 in Table III) is a by-product derived (in the manufacture of nicotinic acid) from the oxidation of nicotine with nitric acid, it is altogether diflerent than nicotine in its effect in the nickel bath. Nicotine is one of the most,

harmful materials from the standpoint of embrittlement of the plate that can be added to a nickel bath, because even about 1 mg./l. will start to darken the low current density plate and make very brittle the bright plate obtained with obenzoyl sulflmide in the bath, and in concentrations of about 6 mg./1. the plate will be quite dark and so exceedingly brittle and strained it will crack of itself despite the presence of o-benzoyl sulfimide in the bath.

It is possible to use various substituting groups on the carbon of the rings of the N-alkyl pyridiniumand quinolinium pyrazoles, e. g. nitro. halogen, sulfonamide, methyl, cyano, acid amide, methyl carboxylic ester, methanol and aldehydo groups.

This application is a continuation-in-part of mv application Serial No. 595.881, filed May 25, 1945, which has become abandoned.

I claim:

1. A bath for electrodepositing bright nickel comprising an aqueous acid solution comprising essentially a material selected from the group consisting of nickel chloride, nickel sulfate, a mixture of nickel sulfate and nickel chloride, a mixture of nickel sulfamate and nickel chloride, a mixture of nickel fluoborate and nickel chloride, a mixture of nickel fluoborate and nickel sulfate. a mixture of nickel sulfate. nickel chloride, and nickel fluoborate, and a mixture of nickel fluoborate and nickel sulfamate, said solution also containing an organic pyrazole compound soluble in the solution selected from the group consisting of N-alkyl (from one to six carbon atoms) pyridinium pyrazoles and quinolinium pyrazoles together with an aryl compound soluble in the bath and selected from the group consisting of benzene sulfonamides, benzene sulfonimides, benzene sulfonic acids, and naphthalene sulfonic acids, said organic pyrazole compound being dissolved in the solution in a concentration falling within a range of from .001 gram per liter to .02 gram per liter of solution and said aryl compound being dissolved in said solution in a concentration falling within a range of from .02 gram per liter of solution to saturation.

2. The bath set forth in claim 1 wherein the pyrazole compound is N-alkyi (one to six carbon atoms) 4-nitro 5-(-3'-pyridinium) pyrazole.

3. The bath set forth in claim 1 wherein the pyrazole compound is N-alkyl (one to six carbon atoms) 3-nitro 5-(-3'-pyridinium) pyrazole.

4. A method for electrodepositing bright nickel comprising the step of electrodepositing bright nickel from an aqueous acid solution comprising essentially a material selected from the group consisting of nickel chloride, nickel sulfate, a mixture of nickel sulfate and nickel chloride, a mixture of nickel sulfamate and nickel chloride, a mixture of nickel fluoborate and nickel chloride, a mixture of nickel fluoborate and nickel sulfate, a mixture of nickel sulfate, nickel chloride, and nickel fluoborate, and a mixture of nickel fluoborate and nickel sulfamate, said solution also containing an organic pyrazole compound soluble in the solution selected from the group consisting of N-alkyl (from one to six carbon atoms) pyridinium pyrazoles and quinolinium pyrazoles together with an aryl compound soluble in the bath and selected from the group consisting of benzene sulfonamides, benzene sulfonimides, benzene sulfonic acids, and naphthalene sulfonic acids, said organic pyrazole compound being dissolved in the solution in a concentration falling within a range of from .001 gram per liter to .02 gram per liter of solution and said aryl compound being dissolved in said solution in a concentration falling within a range of from .02 gram per liter of solution to saturation.

HENRY BROWN.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,238,861 Lind et al Apr. 15, 1941 2,255,057 Holt Sept. 9, 1941 2,315,802 Lind et al. Apr. 6, 1943 2,402,801 Brown June 25, 1946 OTHER REFERENCES Industrial and Engineering Chemistry, vol. 33. PP. 1546, 1547 (1941). 

1. A BATH FOR ELECTORDEPOSITION BRIGHT NICKEL COMPRISING AN AQUEOUS ACID SOLUTION COMPRISING ESSENTIALLY A MATERIAL SELECTED FROM THE GROUP CONSISTING OF NICKEL CHLORIDE, NICKEL SULFATE, A MIXTURE OF NICKEL SULFATE AND NICKEL CHLORIDE, A MIXTURE OF NICKEL SULFAMATE AND NICKEL CHLORIDE, A MIXTURE OF NICKEL FLUOBORATE AND NICKEL CHLORIDE A MIXTURE OF NICKEL FLUOBORATE AND NICKEL SULFATE, A MIXTURE OF NICKEL SULFATE, NICKEL CHLORIE, AND NICKEL FLUOBRATE, AND A MIXTURE OF NICKEL FLUOBORATE AND NICKEL SULFAMATE SAID SOLUTION ALSO CONTAINING AN ORGANIC PYRAZOLE COMPOUND SOLUBLE IN THE SOLUTIN SELECTED FROM THE GROUP CONSISTING OF N-ALKYL (FROM ONE TO SIX CARBON ATOMS) PYRIDINIUM PYRAZOLES AND QUINOLINIUM PYRAZOLES TOGETHER WITH AN ARYL COMPOUND SOLUBLE IN THE BATH AND SELECTED FROM THE GROUP CONSISTING OF BENZENE SULFONAMIDES, BENZENE SULFONIMIDES, BENZENE SULFONIC ACIDS, AND NAPHTHALENE SULFONIC ACIDS, SAID ORGANIC PYRAZOLE COPOUND BEING DISSOLVED IN THE SOLUTION IN A CONCENTRATION FALLING WITHIN A RANGE OF FROM .001 GRAM PER LITER TO .02 GRAM PER LITER OF SOLUTION AND SAID ARYL COMPOUND BEING DISSOLVED IN SAID SOLUTION IN A CONCENTRATION FALING WITHIN A RANGE OF FROM .02 GRAM PER LITER OF SOLUTION TO SATURATION. 